This value records which combination of reverse ATM traffic descriptor parameters was requested for this failed call, per the description, mirroring svcAtmFailedCallAtmTfdType but for the direction back toward the caller rather than forward toward the callee. Because forward and reverse traffic contracts on an SVC can differ (e.g. an asymmetric application), this field lets an admin determine whether a call failed because of its outbound bandwidth request, its inbound (reverse) request, or both, which changes where in the traffic-shaping configuration to look. A failure where only the reverse type looks unusual, with a normal forward type, points specifically at return-path bandwidth handling.